SLC-25A46 regulates mitochondrial fusion through the mitofusin protein FZO-1 and is essential for maintaining neuronal morphology

Mitochondria are dynamic organelles shaped by sequential fission and fusion events. The mitochondrial protein SLC25A46 has been identified as a causative gene for mitochondrial neuropathies. However, the function of SLC25A46 in mitochondrial morphogenesis remains controversial, with several reports suggesting it acts as a mitochondrial fission factor, whereas others propose it as a fusion factor. In this study, employing forward genetics, we identified slc-25A46, a Caenorhabditis elegans ortholog of human SLC25A46, as an essential factor for mitochondrial fusion. Suppressor mutagenesis screening revealed loss-of-function mutations in drp-1, a mitochondrial fission factor, as suppressors of slc-25A46. The phenotype of slc-25A46 mutants is similar to that of mutants in the worm mitofusin ortholog fzo-1, wherein the mitochondrial fusion factor is disrupted. Overexpressing FZO-1 mitigated mitochondrial defects in slc-25a46 mutants, indicating that SLC-25A46 promotes fusion through FZO-1. Disease model worms carrying mutations associated with SLC25A46 exhibited mitochondrial fragmentation and accelerated neurodegeneration, suggesting that slc-25A46 maintains neuronal morphology through regulating mitochondrial fusion regulation.